Drive belt for snow vehicle and suspension therefor

ABSTRACT

An improved lightweight snow vehicle that embodies an improved suspension that permits ease of riding of the vehicle while maintaining good control and handling. The drive belt is supported so that the vehicle has a longer effective length than prior art devices of the same overall length and so that on increased suspension travel a larger portion of it engages the ground. In addition, the body of the vehicle is pivotally supported for leaning movement relative to the rear of the drive belt about a pivot axis that is disposed closely adjacent the ground. The vehicle may, therefore, be ridden like a motorcycle without sacrificing the contact patch between the drive belt and the terrain over which the vehicle is travelling.

BACKGROUND OF THE INVENTION

This invention relates to a drive belt for a snow vehicle and asuspension therefore, and more particularly to a drive belt suspensionthat permits the construction of a small lightweight snow vehicle thatis both easy but also challenging to ride.

The use of snowmobiles as both recreational and functional vehicles fortravelling over snowy terrain is well known. For the most part, theknown type of snowmobiles are relatively large, heavy and expensivemachines. Because of these factors, there is a relatively limited marketfor such machines. Attempts have been made to provide relatively smallone-person snow vehicles that can be easily transported and yet willafford the same recreational and functional advantages as a snowmobile.However, attempts to reduce the size of the snow vehicles to those akinto a motorcycle have not been fully successful. As the size of the snowvehicle is reduced and as manufacturing costs are attempted to bereduced, it is extremely difficult to provide a lightweight snow vehiclewhich is easy to operate safely and which will afford the necessaryriding enjoyment and functionality.

One reason why it has been difficult to provide a satisfactorylightweight snow vehicle is the wide variety of terrain over which suchvehicles travel. Snow vehicles may encounter deep powdery snow, hardpacked snow, ice and even in some instances hard pavement or bareground. In addition, it is not at all uncommon that the terrain overwhch the vehicle travels may vary greatly in grade. In addition, thevehicle must be capable of sudden changes in direction to avoid impactwith partially concealled obstacles. The suspension systems provided forthe drive belt of lightweight snow vehicles heretofore has beenincapable of accommodating such a variety of conditions and terrains.

It is, therefore, a principal object of this invention to provide animproved drive belt suspension system that permits the construction ofan easily operated yet highly stable, lightweight snow vehicle.

It is another object of ths invention to provide the suspension systemfor the drive belt of a snow vehicle that is adapted to provide goodperformance over a wide variety of conditions.

It is yet a further object of this invention to provide a snow vehicledrive belt suspension that provides good handling and will inspireoperator confidence.

SUMMARY OF THE INVENTION

This invention is adapted to be embodied in a small, lightweight snowvehicle having frame means, a front ski supported for steering movementby said frame means, an endless drive belt and power means for drivingsaid drive belt. The drive belt has a drive portion that is positionedfor engaging the terrain over which the vehicle is operated for drivingthe vehicle therealong. In accordance with this feature of theinvention, suspension means support the drive belt and frame means forrelative pivotal movement about an axis that extends generallytransversely relative to the longitudinal axis of the vehicle from aposition wherein the driving portion of the drive belt is at asubstantial angle to the terrain when the suspension means is notheavily loaded so that only the rearwardmost portion of the drive beltdrive portion engages the terrain so as to give the vehicle a greatereffective length than if the entire drive belt contacted the terrainunder all conditions. As the loading increases, the drive belt driveportion is pivotally moved so as to bring a greater portion of it intoengagement with the terrain.

In accordance with another feature of the invention, the suspensionmeans comprises a lever supported for movement about a first pivot axison the frame, suspension means and means including a pivotal connectionbetween the lever and the suspension means for loading the suspensionmeans upon pivotal movement of travel. A link has an operative pivotalconnection to the drive belt and to the lever for pivoting the lever andloading the suspension means upon relative movement upon the drive beltand the frame.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a snow vehicle constructed inaccordance with an embodiment of this invention and showing the vehicleas it appears when travelling over relatively firm terrain and under anormal load.

FIG. 2 is an enlarged cross-sectional view, taken generally along theline 2--2 of FIG. 1, and shows the driving arrangement for the drivebelt.

FIG. 3 is a cross-sectional view taken along the line 3--3 of FIG. 2.

FIG. 4 is an enlarged view taken generally in the direction of the arrow4 in FIG. 1 and shows the rearwardmost suspension of the drive belt.

FIG. 5 is a cross-sectional view taken along the line 5--5 of FIG. 4.

FIG. 6 is a perspective view showing the details of the rear beltsuspension.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first to FIG. 1, a lightweight snow vehicle constructed inaccordance with an embodiment of the invention is identified generallyby the reference numeral 11. The vehicle 11 includes a frame assembly,indicated generally by the reference numeral 12. Although in theillustrated embodiment the frame assembly 12 is depicted as being madeup of a welded tubular assembly, it is to be understood that variousother types of frame configurations can be employed. Furthermore, manyfeatures of the invention can be used in snow vehicles of the type whichdo not use a frame per se but rather employ a body construction whichforms a combined body and frame. When the word "frame" is used hereinand in the claims, it is intended to cover all of such types ofconstructions.

The frame 12 includes a head tube 13 which journals a steering shaft 14to which a steering handlebar 15 is affixed in any known manner. A frontski, indicated generally by the reference numeral 16, is supported forrotation with the steering shaft 14 and for suspension travel relativeto the frame 12 by means of a front suspension unit, indicated generallyby the reference numeral 17.

The ski 16 and front suspension unit 17 may be of the type as disclosedin my co-pending U.S. patent application entitled "Ski for Snow Vehicleand Suspension Therefor", Ser. No. 312,335, filed Oct. 16, 1981 andassigned to the Assignee of this invention. Reference may be had to thatapplication, which is incorporated herein by reference for a descriptionof these components. Briefly stated, the ski 16 is preferably formedfrom a runner of non-metallic construction having one or more downwardlyextending ribs 18 formed from a harder, metallic configuration toprovide wear resistance and directional stability when travelling overhard surfaces such as ice.

The front suspension 17 includes a tubular damping and suspensionelement 19 that carries the ski 16 for pivotal movement about agenerally transversely extending axis. A pair of pivotally connectedforks 21 and 22 permit telescopic movement of the ski 16 relative to thesteering shaft 14 while at the same time restrain the ski 16 forsteering movement with the steering shaft 14.

A seat 23 is supported on the frame 12 in any suitable manner.Preferably the seat 23 is pivotally supported on the frame 12 andconceals a gas tank (not shown) that is carried by the frame 12 beneaththe seat 23.

A driving unit, indicated generally by the reference numeral 24, issupported at the forward end of the frame 12. The driving unit 24includes an internal combustion engine 25, which may be of any knowntype, but is preferably of the single cylinder, two-cycle typeconsistent with the main objectives of the vehicle 11. The engine 25drives an output pulley 26 via a centrifical clutch. Preferably, theengine, clutch and an incorporated starter assembly are of the type asdescribed in my co-pending application entitled "Starting ArrangementFor Internal Combustion Engine", Ser. No. 312,334, filed Oct. 16, 1981and assigned to the Assignee of this application. As disclosed in thatapplication, this starting, clutch arrangement permits an extremelycompact assembly which is, also, consistent with the objects of thisinvention.

The engine driven pulley 26 drives an input pulley 27 of a continuouslyvariable transmission, indicated generally at 28, via a drive belt 29.The continuously variable transmission 28 may be of any suitable type.The continuously variable transmission has an output sprocket 31 thatdrives a chain 32 which, in turn, drives an input sprocket 33 of a finaldrive coupling, indicated generally by the reference number 34 and to bedescribed in more detail.

The drive coupling 34, in turn, drives an endless drive belt, indicatedgenerally by the reference numeral 35. The drive belt 35 is trainedaround the input of the coupling 34 and, in the illustrated embodiment,a bogie type suspension including a pair of rear guide rollers 36 andintermediate pairs of rollers 37 and 38 that are supported by a guidebar 39. The rearward portion of the guide bar 39 is suspended relativeto the frame 12 by means of a rear suspension assembly, indicatedgenerally by the reference numeral 41 and to be described in moredetail. Although the invention is described in conjunction with a bogietype of suspension, it is to be understood that it is equallysuspectible of use with a guide rail type drive belt arrangement.

Referring now additionally to FIGS. 2 and 3, the driving connection 34includes a driving type of constant velocity joint, indicated generallyby the reference numeral 42, which may be of any known type that permitsconstant velocity driving relationship between an input shaft and anoutput shaft while permitting substantial degrees of angular movementtherebetween. Although one type of joint suitable for this purpose hasbeen illustrated and will be described, it should be understood that anyof the known joints of this type may be used in conjunction with theinvention.

The coupling 34 includes an input shaft 43 to which the driving sprocket33 is affixed in a known manner, as by means of a keyway connection (notshown). The shaft 43 is supported, in the illustrated embodiment, abouta fixed axis on the frame 12 by means of mounting plates 44, only one ofwhich appears in the drawings, and an anti-friction bearing 45. Affixedcentrally to the shaft 43 is an inner race 46 of the drive joint 42. Therace 46 is formed with a plurality of arcuate guide tracks 47, each ofwhich receives a ball 48. The balls 48 may be interconnected and held inspaced relationship by a cage (not shown). The outer peripheries of theballs 48 are engaged in guide tracks 49 of an outer race 51 of thecoupling 42. Again, the tracks 49 are arcuate in the opposite sense tothe inner race tracks 47 so as to accommodate a wide degree of angularmovement between the inner and outer races 46 and 51 about a planeperpendicular to the plane of FIG. 2 without adversely affecting thedriving relationship between the inner and outer races.

The outer race 51 is non-rotatably coupled to a driving drum, indicatedgenerally by the reference numeral 52, which has lugs 53 that engagecorresponding recesses in the drive belt 35 so as to drive it in a knownmanner. The drive drum 52 is supported at opposite side adjacent thelugs 53 by means of bearing assemblies 54. The bearing assemblies 54 arerotatably supported by means of a cylindrical member 56 that is affixedin any suitable manner to the guide bar 39.

In the embodiment as thus far described, the front drive arrangement 34for the drive belt 35 is such that the input shaft 43 is supported abouta fixed rotational axis relative to the frame 12. The drive belt 35 may,however, pivotally move about a transverse axis as will be described inmore detail, so that the frame 12 may actually be leaned by the operatorwhen negotiating a turn. That is, the driving shaft 43 is not suspendedfor suspension movement relative to the frame assembly, 12 and,accordingly, the front portion of the drive belt 35 will undergo nosuspension travel relative to the frame. The invention may, however, beemployed with an arrangement wherein the input shaft 43 is alsosuspended relative to the frame 12 so that there will be suspensiontravel at both the front and rear ends of the drive belt 35. If such asuspension arrangement is employed for the front of the drive belt 35, adriving coupling of the constant velocity type like the coupling 42should still be provided so that the leaning motion of the frame 12relative to the drive belt 35 will still be retained. The way that sucha front suspension can be incorporated into the construction asdescribed is believed to be well within the scope of those skilled inthe art and, for that reason, such an arrangement has not beenillustrated and will not be described in any more detail.

The rear suspension 41 will now be described in detail by particularreference to FIG. 1 and FIGS. 4 through 6. The guide bar 39 is providedwith a notch or recess 57 which extends toward its lower periphery andpreferably as close as possible to the drive belt 35. The notch 57 isformed in the portion of the guide bar 39 between the pivotal supportsof the rollers 36 and 38. A connecting member 58 is received in thenotch 57 and is affixed in a suitable manner to the guide bar 39. Theconnecting member 58 supports a pivot pin 59 which, in turn, ispivotally connected to a supporting link 61. The link 61 is, therefore,pivotally connected to the guide bar 39 about an axis defined by thepivot pin 59, which axis extends in a generally longitudinal directionrelative to the vehicle 11 and which is placed as close as possible tothe lower surface of the drive belt 35.

A crossbar 62 of a link assembly, indicated generally by the referencenumeral 63, is affixed as by welding to the upper end of the link 61.The crossbar 62 extends transversely outwardly beyond the outerperiphery of the drive belt 35. A pair of links 64 are pivotallyconnected, in any suitable manner, at one of their ends to the rod 62.The opposite ends of the links 64 are pivotally connected to a crossbar65 which is, in turn, pivotally connected to a fabricated bellcrankassembly, indicated generally by the reference numeral 66. The bellcrankassembly 66 includes a first pair of links 67 that are pivotallyconnected at one of their ends to the crossbar 65. The opposite ends ofthe links 66 are pivotally supported relative to the frame 12 by meansof a pivot shaft 68. Rigidly affixed to the links 67 but spaced inwardlytherefrom is a pair of angularly extending links 69. The links 69 arealso pivotal relative to the crossbar 65 and are connected rigidly attheir forwardmost end to a bridging member 71 of the bellcrank assembly66 which is also affixed to the forward ends of the links 67.

The bridging member 71 and forward ends of the links 69 are pivotallyconnected by means of a pin 72 to a suspension element, indicatedgenerally by the reference numeral 73. The suspension element may be ofany known type and is illustrated as being of a combined spring andshock absorber assembly. That is, the suspension element 73 includes acylinder housing 74 to which the pivot pin 72 is pivotally connected.The cylinder housing 74 also has a collar 75 that loads one end of acoil spring 76. The assembly 73 also includes a piston rod 77 that ispivotally connected at its forward end by means of a pivot pin 78 to theframe 12 beneath the seat 23. This connection also includes a loadingarrangement for restraining the opposite end of the coil spring 76against axial movement. Upon suspension travel, the spring 76 will becompressed and the cylinder assembly 74 will move axially relative tothe piston rod 77 and the piston (not shown) carried thereby. The unit73 includes suitable hydraulic orifices and check valves so as tohydraulically damp the suspension travel, as is well known with suchunits.

The frame assembly 12 is pivotal relative to the guide rail 39 and drivetrack 35 at the rear portion thereof about the pivot axis as defined bythe pivot pin 59. As has been noted, it is desirable to maintain thispivot axis as close as possible to the point of engagement of the rearportion of the drive belt 35 with the ground. By doing so, the ridingcharacteristics are greatly increased and the leaning of the operatorinto a curve provides a better feel since the leaning is about a pointvery close to the close of contact of the drive belt 35 with the terrainover which the vehicle is travelling. An arrangement is provided so asto insure that the effective pivotal movement of the frame 12 relativeto the forwardmost portion of the guide rail 39 is also at the mostdesirable location relative to the forwardmost portion of the drive belt35.

If it is desirable to locate the front pivot point at a point other thanthe joint 42, a stabilizer mechanism shown in most detail in FIGS. 1 and2 may be provided. The stabilizer mechanism includes a link 81 that ispivotally connected in any known manner as by a joint 82 at one of itsends to a member such as a threaded post affixed to the frame 12. Theopposite end of the link 81 is connected by means of a pivotalconnection such as a pivotal joint 84 to the guide rail 39 at a pointwhere it is desired to locate the front pivot axis between the frame 12and drive belt 35. The link 81 and the location of the pivot joint 84have the effect of transferring the effective pivotal axis of the frame12 relative to the forwardmost portion of the guide rail 39 to the pointwhere the pivotal connection 84 lies.

In order to provide some damping of the pivotal movement of the frame 12relative to the drive belt 35, any suitable damping mechanism, as by themeans of the frictional damper, indicated generally by the referencenumeral 85, may be provided. The frictional damper 85 may be of anysuitable type and as such can comprise a plate that is affixed to theguide rail 39 and a plate that is affixed for pivotal movement with thelink 61 and means to provide frictional contact between these twoplates. Other suitable mechanisms may be employed for achieving suchdamping.

Operation

The suspension arrangement employed and the pivotal support of the framerelative to the rear drive belt have been chosen so as to give thevehicle 11 riding characteristics on the snow which will be comparableto the riding of a motorcycle on solid ground. That is, when negotiatinga curve, the operator can lean the body of the vehicle so as to improvehandling. However, the arrangement is such that leaning of the operatorwill not result in any loss of contact area between the drive belt 35and the terrain over which the vehicle 11 is travelling. This has beenfound to significantly improve rideability and, further, to make thevehicle 11 easier to learn to ride by a novice. Furthermore, thesuspension of the drive belt 35 is such that the vehicle 11 has arelatively long effective wheel base. This offers further improvementsin handling. The rear axis about which the vehicle leans will still bevery close to the point of engagement of the drive belt 35 with theterrain regardless of the degree of suspension loading.

Considering now the situation when travelling over the ground when in astraight direction and when lightly loaded, the suspension element 73 isdesigned so that the flight of the drive belt 35 between the rollers 36and 37 will be at a fairly substantial angle relative to the ground, asseen in FIG. 1. As a result, only the rearwardmost portion of the drivebelt 35 will engage the terrain and the vehicle 11 has a relatively longeffective wheel base under this condition. When loading increases, therearward portion of the guide rail 39 will tend to swing upwardlycausing the link 64 to load the bell crank assembly 66 and cause itspivotal movement about the pivot pin 68. Such pivotal movement causesloading of the suspension element 73 to compress the spring 76 andprovide hydraulic damping. As this pivotal movement occurs, it should bereadily apparent that the angle between the flight of the drive belt 35between the rollers 36 and 37 relative to the ground will decrease and agreater contact patch will be provided.

When the vehicle 11 is negotiating a turn, the operator turns thehandlebars 15 to steer the front ski 16. As has been noted, the ski 16is configured so that it will provide a good grip on a wide variety ofsurfaces so provide an adequate steering force. In addition, theoperator may lean the frame 12 into the direction of the curve beingnegotiated. This leaning movement causes pivotal movement of the frame12 relative to the drive belt 35 about the axis defined by the pivot pin59 and the joint 84. If the stabilizer link 81 is not employed, thefront leaning pivot point will lie at the joint 42. In either case uponpivotal movement the driving relationship between the input shaft 43 andthe drive belt 35 will be maintained due to the constant velocity joint42.

It should be readily apparent that an arrangement has been provided forsuspending the drive belt of a lightweight snow vehicle from a frame insuch a way that good riding characteristics may be achieved over a widevariety of terrains and with changing grades. The suspension affords anincreasing amount of contact between the drive belt and the terrain overwhich the vehicle is travelling when the loading on the vehicleincreases. This improves not only traction but permits the vehicle tohave a longer effective length. As has been noted, in the illustratedembodiment, the forwardmost portion of the drive belt is not supportedfor suspension travel relative to the frame. The invention, however, issusceptible of use in an arrangement where both the forward and rearwardportions of the drive belt are capable of suspension travel. Variousother changes and modifications may be made without departing from thespirit and scope of the invention, as defined by the appended claims.

I claim:
 1. A snow vehicle having a frame, front ski means supported bysaid frame for steering movement, an endless drive belt, drive means fordriving said drive belt, and suspension means for supporting said drivebelt for suspension movement relative to said frame, said suspensionmeans comprising a lever supported for pivotal movement about a firstpivot axis on said frame, a suspension element, means including apivotal connection between said lever and said suspension element forloading said suspension element by the pivotal movement of said lever, alink, means providing a relative pivotal connection by the one end ofsaid link and said drive belt, and means pivotally connecting the otherend of said link to said lever for pivoting said lever upon movement ofsaid drive belt relative to said frame for loading the suspensionelement upon such relative movement.
 2. A snow vehicle as set forth inclaim 1 further including guide means for defining a path of movementfor the drive belt, the suspension means being interposed between saidguide means and the frame.
 3. A snow vehicle as set forth in claim 2wherein the guide means has a first, forward pivotal connection to theframe and the suspension means is interposed between the rearwardportion of the guide means and the frame and permits the drive belt topivot about said first pivotal connection.
 4. A snow vehicle as setforth in claim 3 wherein the link comprises a bell crank having oneportion thereof pivotally supported on the frame, the pivotal connectionbetween said bell crank and the suspension element being at the one armof said bell crank and the pivotal connection between the link and saidbell crank being at the other arm of said bell crank.
 5. A snow vehicleas set forth in claim 4 wherein the suspension element comprises acombined shock absorber spring assembly.
 6. A snow vehicle as set forthin claim 5 wherein the suspension means is effective to cause onlycontact of the rearwardmost portion of the drive belt with the terrainwhen the vehicle is lightly loaded, yielding of the suspension meansbeing effective to cause a greater portion of the drive belt to contactthe terrain.
 7. A snow vehicle having a frame, front ski means supportedby said frame for steering movement, a drive belt, guide means fordefining a path of movement for said drive belt including a generallyplaner driving length, drive means for driving said drive belt, firstsuspension means for supporting a forward portion of said guide meansrelative to said frame, said first suspension means being effective toestablish a forward, generally horizontally extending transverse axisabout which said guide means may pivot, and second suspension means forsuspending a rearward portion of said guide means for relative movementrelative to said frame, said suspension means being contacted andarranged so that said driving length of said drive belt is disposed atsuch an angle to the terrain that only the rearwardmost portion thereofengages the ground when said suspension means is at a normal positionand for providing a lesser angle between said drive length as saidsuspension means is loaded for increasing the contact area between saiddrive belt and the ground.
 8. A snow vehicle as set forth in claim 7wherein the guide means comprises a guide bar and the suspension meansis interposed between the guide bar and the frame.
 9. A snow vehicle asset forth in claim 8 wherein the first suspension means provides a fixedaxis relative to the frame.
 10. A snow vehicle as set forth in claim 8wherein the second suspension means comprises a suspension element andlink means for loading said suspension element upon movement of therearwardmost portion of the guide means relative to the frame.
 11. Asnow vehicle as set forth in claim 10 wherein the link means comprises abell crank pivotally supported on the frame and having a first armpivotally connected to the guide means and a second arm pivotallyconnected to one end of the suspension element.